Hemlock woolly adelgid attacking southern Maine

Sunday

The hemlock woolly adelgid, or HWA, is a microscopic female insect that reproduces by parthenogenesis, as many as 20,000 eggs a year, and it has made its way into the forests and private property of wide swaths of Kittery, Eliot, South Berwick and York.

For anyone who has enjoyed the woods and appreciates the rich ecosystem in the Mount Agamenticus region, where there are a number of infested stands, the reasons to be concerned are many. Maine Forest Service entomologist Allison Kanoti said hemlocks are a key part of that system. They provide food for moose, winter cover for wildlife and a required habitat for many species of migratory song birds.

Those who enjoy fishing know hemlocks tend to grow in riparian areas, providing shade for the insects that brook trout, for instance, love, Kanoti said. They're also just beautiful evergreens, she said, worthy of saving if for no other reason than that. And hemlock woolly adelgids are out to kill them, she said. There are about 160,000 acres of hemlock-dominated forest in southern coastal Maine and about 10,000 acres of infested hemlock in the area. The death is not quick, though, but a slow, deteriorating one that can take up to 10 years.

Kanoti, recently in York to check on the advance of HWA, came up to what looked like a healthy hemlock, sprouting new pale green needle clusters at the end of each branch.

One branch, though, she points out, has no such cluster. Flipping it over, she points to numerous small white clumps — pregnant HWAs. The released eggs in the sacks soon become minute "crawlers" about the size of a grain of sand, which get sustenance by placing their needle-like mouths on a bit of branch and sucking out the nutrients.

They have two life cycles a year, are dormant only in the hot summer months, and they're spreading — often by birds who sit in the branches and carry away the crawlers to a new hemlock somewhere else.

These adelgids are Japanese in origin, said Kanoti, traveling to the United States on ornamental trees bound for nurseries. The first ones were detected in the Richmond, Va., area in 1951, and they've been making a slow, steady path up the East Coast since.

Kanoti said there was an "explosion" of HWA in the mid-1980s in Connecticut and into Massachusetts, where large areas of hemlocks are now devastated.

Now, they've traveled to the most southern reaches of Maine. The first reported case was on Gerrish Island in Kittery in 2003. They've since been spotted east and west of Route 1 in Kittery; along Brixham Road and Route 103 and south of York Pond in Eliot; and north of York Pond and in the routes 236 and 91 area of South Berwick.

In York, it is the Mount Agamenticus region that's been hit. For the past three years, the Maine Forest Service has been working with the York Water District, which owns thousands of acres of land in the Chase's Pond watershed.

On several test stands on district land, the Maine Forest Service has been releasing laboratory-reared "predator beetles," tiny lady beetles, who love to feed on HWAs. They're Japanese, too.

This year alone, the forest service released 3,750 in York, and has released 6,000 since 2007.

"We already know the beetles are reproducing," she said. "We've seen the larvae."

But this biological control is going to take time. And time is on the side of the HWA. Three years ago when Kanoti started monitoring an infested stand, 14 percent of the hemlocks were infested. Last year, it was 20 percent. This year, it's 28 percent.

As it turns out, Kanoti said, Maine, New Hampshire and Vermont are all facing this problem in their southernmost reaches, so they pass data back and forth. But the fact is, she said, no one knows how many beetles will be needed to combat the adelgids or when to release them for maximum effect.

"We're going on faith and burgeoning science," she said.

Further complicating matters, there is beginning to be some evidence that the adelgids, who have not been particularly cold tolerant, are building up immunity to southern Maine's climate and could be heading farther north. They've been spotted as far north as Harpswell, she said.

She said homeowners with hemlocks should check their trees this time of year for signs of adelgids. She said there are chemical treatments, but they kill good insects as well. She said if people see signs of HWAs on their trees, they are encouraged get in touch with her office at the Maine Forest Service for help.

How to help

To report suspected hemlock woolly adelgid, call the MFS lab at (207) 287-2431 or e-mail allison.m.kanoti@maine.gov. For more information on HWA, visit www.maine.gov/doc/mfs/HemlockWoollyAdelgid.htm.

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